onHorizo ntalDragEnd DragEndDetails.primaryVelocity的问题

Question

一般来说，我对android开发非常陌生，如果其中一些是显而易见的答案，请原谅我。

我正在尝试实现向左滑动/向右滑动功能，以在应用程序的页面之间进行交换。但是，我遇到了检测速度并使用它来确定是否进行了左/右交换的问题。

这是我的代码，为清楚起见，保留了调试器说明：

onHorizontalDragStart: (DragStartDetails details) {
  print("Horizontal Drag Start - preflop.");
},
onHorizontalDragDown: (DragDownDetails details) {
  print("Horizontal Drag Down - preflop.");
},
onHorizontalDragUpdate: (DragUpdateDetails details) {
  print("Horizontal Drag Update - preflop. Velocity Delta: " + details.primaryDelta.toString());
},
onHorizontalDragEnd: (DragEndDetails details) {
  // TODO: Check velocity for non-zero but still too slow to swap?
  if (details.primaryVelocity >= 0) {
    print("Horizontal Drag End - preflop movement cancelled. Velocity: " + details.primaryVelocity.toString());

    return;
  }
  else {
    print("Horizontal Drag End - preflop. Velocity: " + details.primaryVelocity.toString());

    Navigator.push(
      context,
      MaterialPageRoute(builder: (context) => Flop()),
    );
  }
}

    onHorizontalDragStart: (DragStartDetails details) {
      print("Horizontal Drag Start - flop.");
    },
    onHorizontalDragDown: (DragDownDetails details) {
      print("Horizontal Drag Down - flop.");
    },
    onHorizontalDragUpdate: (DragUpdateDetails details) {
      print("Horizontal Drag Update - flop. Velocity Delta: " + details.primaryDelta.toString());
    },
    onHorizontalDragEnd: (DragEndDetails details) {
      // TODO: Check velocity for non-zero but still too slow to swap?
      if (details.primaryVelocity <= 0) {
    print("Horizontal Drag End - flop movement cancelled. Velocity: " + details.primaryVelocity.toString());

    return;
      }
      else {
    print("Horizontal Drag End - flop. Velocity: " +
        details.primaryVelocity.toString());

    Navigator.pop(context);
      }
    }

当它正常工作时，这是我得到的调试输出：

I/flutter (17305): Horizontal Drag Down - preflop.
I/flutter (17305): Horizontal Drag Start - preflop.
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -5.712890625
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -5.336216517857167
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -7.998046875
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -8.763950892857167
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -11.42578125
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -11.049107142857167
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -11.049107142857167
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -13.334263392857139
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -11.42578125
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -8.763950892857139
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -7.998046875
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -5.336216517857139
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -3.427734375
I/flutter (17305): Horizontal Drag Update - preflop. Velocity Delta: -4.5703125
I/flutter (17305): Horizontal Drag End - preflop. Velocity: -710.2030737630879

我面临两个主要问题。首先，有时即使我正确地刷卡，primaryVelocity仍返回零。可以通过跟踪onHorizontalDragUpdate并查看生成的onHorizontalDragEnd来见证这一点。现在，我了解到，如果我拖动然后停止然后放开光标，逻辑上结束速度将为零-但是在这种情况下，我没有感觉到暂停-只是拖动并释放。

I/flutter (17305): Horizontal Drag Down - flop.
I/flutter (17305): Horizontal Drag Start - flop.
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -6.85546875
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -8.763950892857167
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -7.998046875
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -9.906529017857167
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -9.140625
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -8.763950892857167
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -7.998046875
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -5.336216517857139
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -6.85546875
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -4.5703125
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -4.193638392857139
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -2.28515625
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -2.28515625
I/flutter (17305): Horizontal Drag End - flop movement cancelled. Velocity: 0.0

另一个问题是，有时primaryVelocity的符号似乎不正确。例如，尽管onHorizontalDragUpdate的值为primaryDelta为负，但所得的onHorizontalDragUpdate的速度为正值：

I/flutter (17305): Horizontal Drag Down - flop.
I/flutter (17305): Horizontal Drag Start - flop.
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -12.191685267857167
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -11.42578125
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -14.476841517857167
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -13.334263392857139
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -11.049107142857139
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -6.85546875
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -6.85546875
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -4.193638392857139
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -3.427734375
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -3.427734375
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -1.142578125
I/flutter (17305): Horizontal Drag Update - flop. Velocity Delta: -1.142578125
I/flutter (17305): Horizontal Drag End - flop. Velocity: 58.203062840330496

任何建议将不胜感激。让我知道我是否可以提供其他代码来帮助回答问题。谢谢！

编辑

根据Ulas的建议，我更新了所有插件/ IDE。似乎第一个问题已解决-我不再获得0.0的速度。

但是，我仍然遇到第二个问题：

I/flutter (18942): Horizontal Drag Down - flop.
I/flutter (18942): Horizontal Drag Start - flop.
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -6.478794642857167
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -7.998046875
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -8.763950892857167
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -9.140625
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -9.906529017857167
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -10.283203125
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -13.334263392857167
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -13.334263392857167
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -14.476841517857139
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -12.191685267857139
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -10.283203125
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -12.191685267857139
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -10.283203125
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -8.763950892857139
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -6.85546875
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -5.336216517857139
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -4.5703125
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -3.427734375
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -3.427734375
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -1.9084821428571388
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: -1.142578125
I/flutter (18942): Horizontal Drag Update - flop. Velocity Delta: 0.0
I/flutter (18942): Horizontal Drag End - flop. Velocity: 220.44058450541567

Answer 1

我的代码没有获得任何0.0的速度，您可以尝试其他波动通道，例如beta并升级最新版本吗？>